Many prior land vehicle navigation route apparatus are known in which a desired route between a start location and a desired destination location are calculated via fixed road path segments. In such prior systems, typically a vehicle operator will specify his desired destination location. The prior system then determines the start position of the vehicle, or this information may also be input to the system by the vehicle operator. Prior systems then use stored road map data to select an optimum route between the start and destination location. This optimum route is selected according to a predetermined criterion which strives for either minimum distance or minimum time. The route is calculated by considering various characteristics associated with the road path segments that may be utilized in the route wherein such characteristics are stored along with the map data that defines the location of the road path segments.
Many of the above noted prior navigation systems allow the vehicle operator to specify route preferences for the route to be calculated. Thus, for example, the vehicle operator may specify that he prefers multiple lane road paths and expressways, and the navigation apparatus will accommodate these desires in calculating the navigation route. Some systems also allow the vehicle operator to specify detours which are defined as specific road segments or areas to be avoided during the navigation route. Typically, all of these preferences and detours (exclusions) are specified prior to the calculation of a navigation route. The navigation apparatus then proceeds to calculate the single optimum navigation route between the start and destination locations.
If the vehicle operator does not like the calculated optimum route, he then has to enter additional preference or detour (exclusion) information and the route calculation will then take place all over again. Since typically the route calculation step is a lengthy time consuming step and calculation of an alternate route occurs after the operator specifies additional information, this slows down the trip planning of the vehicle operator. Also, if the vehicle operator does not like a second calculated route but prefers the first calculated route, he must then enter additional information to restore the original preferences and detours used to calculate the initial route. In other words, the prior route navigation apparatus calculates one optimum route for one set of vehicle operator specified inputs. If the vehicle operator merely asks his navigation system to calculate another route without changing any input, the navigation apparatus will compute the exact same route. If the vehicle operator modifies the input data, then a new route can be calculated, but in order to select the previous route he has to implement an additional modification of input data to recalculate and then reselect the original calculated route. Also, the vehicle operator may not accurately recall differences between two sequentially calculated routes and may therefore have a hard time intelligently selecting which route he desires.
What is needed is a navigation route apparatus which minimizes the problems mentioned above and allows intelligent vehicle operator selection of a desired route without any undue delay in providing the vehicle operator this option.